Re: Numeric for loop with rationals

[Sean Conner <sean@...>]

It was thus said that the Great Charles Heywood once stated:
> I am confused on why you think you can't:
> 
> Lua 5.3.4  Copyright (C) 1994-2017 Lua.org, PUC-Rio
> > function one() return 1 end
> > function two() return 2 end
> > function ten() return 10 end
> > for i=one(), ten(), two() do print(i) end
> 1
> 3
> 5
> 7
> 9
> >

  That only works for numbers.  Soni would like a custom type, like
rationals, as in the first example:

	for x = r(1,10) , r(10,10) , r(1,10) do
	  print(x)
	end

  The stock numeric for in Lua is defined as:

     do
       local var, limit, step = tonumber(e1), tonumber(e2), tonumber(e3)
       if not (var and limit and step) then error() end
       var = var - step
       while true do
         var = var + step
         if (step >= 0 and var > limit) or (step < 0 and var < limit) then
           break
         end
         local v = var
         block
       end
     end

  The conversion of var, limit and step to numbers is preventing the use of
custom types that cannot be converted to numbers:

	for i = "1" , "10" , "2" do print(i) end

  -spc